The present invention relates to an apparatus for automatically opening and closing a door of a vehicle body which is located in a manufacturing process in a plant.
In a process for manufacturing a vehicle in a plant, it is sometimes necessary to automatically open and close a door of a vehicle body. For instance, an automatic opening and closing operation of a vehicle door is necessitated when an inside of a door is painted in a vehicle body painting process. In this circumstance, a door lock device is conventionally mounted on a vehicle door to inhibit an inadvertent opening of the vehicle door, occurred at the time when a vehicle body is transferred by a conveyor. However, a door lock device has to be unlocked before a vehicle door opens. In general, a robot or a special purpose device unlocks a door lock device to open a vehicle door. When a robot or a special purpose device unlocks a door lock device mounted on a vehicle door, an error in position of a transferred vehicle body occurs by the distance within plus or minus 20 mm at the place between an actual transferred position and a predetermined position of a vehicle body in a process for manufacturing a vehicle. Hence, such a robot or a special purpose device includes a position sensor therein, thereby sensing the actual positions of a door lock device and a vehicle door to unlock the door lock device and open and close the vehicle door. However, an apparatus for automatically opening and closing a vehicle door costs a lot. Further, an inaccurate operation of a sensor or a special purpose device may happen to cause it to strike against a door lock device or a vehicle door, thereby resulting in damage to them.